A conventional device of the foregoing type is disclosed in German OS NO. 24 34 899 and serves to intermittently apply a thread-treating medium in the form of a wetting agent or a lubricant onto the thread. During the rotation of the storage disk and the overflow plate, the portion of the thread extending tangentially of the storage disk and from there over the edge of the overflow plate moves in a defined path of rotation. The wiping head extends into such path of rotation. During each spindle rotation, the thread wipes over the wiping head and thereby takes along a certain amount of the thread-treating medium. This then serves to reduce friction between the balloon-limiting means and the thread, which results in reduced wear and also substantially reduces the danger of yarn damage and thread breakage. In the conventional device, the insert consists of a suction member such as a wick, for example, of felt, which reaches from the supply pipe to the port of the opening in the wiping head. The disadvantage of this conventional device is that the amount of the thread-treating medium which exits at the port varies considerably due to the fact that the wicks produce varying capillary actions which cannot be precisely controlled. Furthermore, such suction member inserts are particularly subject to aging, as a result of which their suction capability is reduced.
In a different conventional device for feeding a liquid thread-treating medium to the thread in a double thread twisting machine, as disclosed for example in German OS No. 28 03 488, the wiping head consists of a plurality of thin steel plates which are arranged side-by-side with a small horizontal spacing, the planes of which extend substantially tangentially with respect to the spindle axis and the lower parts of which are immersed in the thread-treating medium. Here, too, the thread-treating medium is moved through by the capillary action induced by the gaps between the steel plates to the upper edges of the plates where it is wiped over by the thread. This device, however, is relatively expensive to manufacture because, in addition to the steel plates, two disks which hold the steel plates and a relatively expensive housing which encloses the wiping head are needed.
The primary purpose of the invention is thus to produce a device for feeding a liquid thread-treating medium to the thread in a double thread twisting machine of the above-mentioned type which is simple in structure and which supplies a precisely predeterminable amount of the thread-treating medium to the thread without aging symptoms over a long period of time.